1. Field of the Invention
This invention relates to a method to confer formaldehyde-resistance to a plant comprising the steps of; introducing gene(s) encoding enzyme(s) involved in the metabolic system of formaldehyde into the plant and having the gene(s) expressed in the chloroplast, thereby the ability to assimilate formaldehyde into an intermediate of the Calvin cycle is conferred to said plant, and to a transgenic plant produced by the method. Moreover, this invention relates to a method to have a plant to absorb environmental formaldehyde comprising the steps of; introducing gene(s) encoding enzyme(s) involved in the metabolic system of formaldehyde into the plant and having the gene(s) expressed in the chloroplast, thereby the ability to assimilate formaldehyde into an intermediate of the Calvin cycle is conferred to said plant, and to a transgenic plant produced by the method.
2. Background Art
Formaldehyde is a chemical substance existing in building materials etc., and it is known to cause sick house syndrome, because formaldehyde effects to human body even if the concentration in the atmosphere is very low. The regulation of environmental standard of formaldehyde is expected to become stricter than before, for example, the use of building materials which release formaldehyde is prohibited according to the amendment of Building Standard Law dated Jul. 1, 2003. Therefore, in view of decreasing the amount of substances involved in environmental pollution (for example phytoremediation using a plant), a method available to remove and to decrease the concentration of environmental formaldehyde has been demanded.
Meanwhile, as a technique to decrease the concentration of environmental formaldehyde by a biological means, a method using a microorganism that can degrade formaldehyde has been known. However, until now, a technique to decrease formaldehyde concentration using a transgenic plant has not been known, which comprising production of the transgenic plant introduced with a gene encoding an enzyme involved in metabolic system of a plant. Moreover, despite that there have been techniques to confer resistance to various stresses to a plant by performing gene recombination in a plant, there has not been an example to incorporate a gene involved in metabolic system, in view of environmental purification.
Meanwhile, as an example of environmental purification using a plant, a method to clean-up dioxin containing medium is known, and the method is characterized in that Ri plasmid derived from Agrobacterium rhizogenes is introduced into a plant of Solanaceae, Cruciferae, Umbelliferae, Chenopodiaceae, Leguminosae, Compositae, or Saxifragaceae to induce the hairy root of the plant, and contacting it with the dioxin containing medium to have the dioxin absorbed or decomposed by the hairy root or by the re-generated plant body (Japanese Patent Publication No. 2000-176433). However, this report is not directed to formaldehyde.
In addition, as a knowledge on the formaldehyde metabolism of a plant, it has been reported that a plant body, in which the expression of glutathione-dependent formaldehyde dehydrogenase (FALDH) derived from Arabidopsis thaliana is manipulated, has been produced (Plant Physiol. 2003). As a result, the intake of formaldehyde was enhanced in a plant body in which FALDH was over-expressed, whereas the intake of formaldehyde was apparently low in a wild-type plant body in which the expression of FALDH had not been manipulated. From this result, it is apparently suggested that FALDH is involved in detoxification of formaldehyde.
Meanwhile, among microorganisms, existence of methylotrophic microorganisms, which can grow using a compound having one carbon (C1 compound) such as methanol has been known. Such microorganism is provided with a metabolic pathway that serves to fix formaldehyde derived from methanol, as a carbon source. Moreover, hexose-6-phsophate synthase and 6-phosphohexulose isomerase are involved in such metabolic pathway of the methylotrophic microorganism.
In connection to this, said gene encoding the enzyme derived from the methylotrophic microorganism is introduced into Burkholderia capacia TM1, which is an organism not having the ability to utilize methanol, and the enzyme is over-expressed in the microorganism. Then it is reported that the intake of formaldehyde is increased and the metabolic pathway to generate formaldehyde by metabolism of vanillic acid is activated (Appl. Environ Microbiol. 2003). Such knowledge indicates that the ability to degrade vanillic acid can be also improved in a non-methylotrophic microorganism through the pathway of hexulose-6-phosphate synthase/6-phosphohexulose isomerase.